1. Field of the Invention
This invention relates to the use of yeast cell debris products in foodstuffs; cosmetics and pharmaceuticals.
2. Description of Related Art
Yeast extract is commercially produced on a large scale by lysis (e.g., hydrolysis, autolysis or plasmolysis) of baker's yeast or brewer's yeast in suitable form or of other fermentation yeasts (e.g., from gasohol production), which results in soluble material and material which is rich in virtually intact cell wall bodies. The latter material is normally removed from the soluble material by centrifugation. The lysis inevitably results in some disruption of the cell walls, such that there is a substantial proportion of virtually intact cell wall bodies, with at least one zone of discontinuity in the cell wall surface region (that is, holes have resulted in the relevant cell walls). The material containing cell wall bodies (known as yeast debris, or colloquially as yeast ref), which has a dark brown color, an unpleasant odor and rapidly putrifies, contains a number of undesirable materials, such as trace elements, coloring agents, hop extracts, tartrates, microorganisms, bacteria, protein slime and a large amount of insoluble components such as yeast cell wall bodies, as well as a certain amount of unlysed whole cells; such yeast debris is normally discarded. The soluble material from which the debris has been separated is normally used for the extraction of useful materials, such as yeast extract.
PCT/GB91/01819 discloses a process of treating yeast debris which produces a purified form of yeast ghosts or shells having substantially intact cell walls (that is, retaining the in vivo morphology of yeast cell walls in yeast debris), but without the yeast cell contents. That is, the yeast ghosts correspond in morphology to that of lysed material (the yeast debris, or ref) and not that of the whole yeast cells; the yeast ghosts comprise essentially yeast beta-glucan.
Yeast beta-glucans are, of course, well known. U.S. Pat. No. 4,810,646 discloses a method of producing yeast beta-glucans, which comprises separating growing Saccharomyces cerevisiae yeast from its growth medium, subjecting the intact whole yeast cells to alkaline digestion to solubilize the protein portion of the cell, and treating the insoluble glucan with acetic acid to alter the beta (1,6) linkages. The resulting whole glucan particles are described in U.S. Pat. No. 4,962,094 as being suitable for use as dietary additives and are said to substantially retain the in vivo glucan three-dimensional molecular structure of the yeast cells from which they are derived. However, the cell walls are effectively destroyed in the method described. In PCT/GB91/01819, the yeast ghosts or shells are obtained from yeast debris without destruction of the cell wall structure.
The term yeast cell ghosts, as used herein, covers yeast ghosts or shells having a proportion of yeast cell wall which is substantially intact.
The present invention is based on applications of the yeast cell ghosts described in PCT/GB91/01819.
It has been found that yeast cell ghosts may be used to produce coloring agents which are insoluble in aqueous media. The coloring agents may be produced from natural substances thus avoiding the use of artificial carriers and/or colorings. The coloring agents may be used in impart color to a variety of materials including foodstuffs, cosmetics and pharmaceuticals.